conductors, you use other colors. but typically the red or the black. >> in the residences, it's black, black and red. and commercial work where you have 12208, it's black, red, blue. and if you go downtown, the 480 volts, it's brown, orange, yellow. boy. >> and one people with us today just asked a question. is there any reason why you can't wire the entire house with the heavier gauge wire rather than just the lighter gauge for the 15 amp circuits and the heavier gauge for the 20 amp cirçoyd, come up here and is there any reason why you can't wire it all with a heavier gauge wire? >> yes. because it's a 15 amp and the yellow is 20 amp. but some people are asking if they can use only yellow. you can do that >> you can overdo. you can't under do it. >> yes.